Copolymers of polysiloxanes and other thermoplastic resins have found wide utility in commercial applications. For example, it is known in the art that polycarbonates can be copolymerized with linear polysiloxanes which are modified with allyl phenolic endgroups. These organopolysiloxane polycarbonate copolymers are disclosed in Vaughn, Jr., U.S. Pat. Nos. 3,419,634 and 3,419,635. Due to the usefulness of such copolymers, new methods for preparing siloxane copolymers are continuously sought after.
Zhou et al., Polymer Bulletin 22, 85-88 (1989) describe the hydrosilation of an alkenyl isocyanate onto cyclic siloxanes containing SiH groups, such as 1,3,5,7-tetramethylcyclotetrasiloxane. However, long reaction times are necessary and poor yields are obtained.
It has now been discovered that novel siloxanes which are endcapped with isocyanate functionalities can be easily prepared and are useful in producing siloxane copolymers with thermoplastics containing alcohol and/or amine substituents. Further, the copolymerization produces no reaction by-products.